The present invention relates to a semiconductor memory and, more particularly, to a technique which may be effectively utilized in, for example, a mask ROM (Read-Only Memory) incorporating an ECC (Error Correcting Code) circuit.
The applicant of this application has previously developed a mask ROM (product name "HN62301") which incorporates an ECC circuit. This mask ROM incorporates an ECC circuit which effects error correction with respect to one bit among 32 bits by employing a Hamming code. Accordingly, the mask ROM is able to correct any error in memory data by virtue of the ECC circuit, which means that it is possible to increase the product yield and improve the reliability.
The above-described mask ROM suffers, however, from the following problem. Since the ECC circuit is arranged such that 32 bits which constitute one input signal are simultaneously processed for error correction, the size of an error correcting circuit is undesirably increased, and this leads to an increase in the size of the ECC circuit. As a result, the chip size is increased about 25%, disadvantageously.